Train help London and Scotland

If I purchase the Britrail pass will it get me from heathrow to my hotel in Croydon? It is difficult to be authoritative because you don't say where your hotel is in Croydon. Is it walking distance from East Croydon Station? If so, I would guess that it might be possible to cobble a trip together that could get you to East Croydon by train from Paddington but it would be difficult and complicated - and take forever. You will probably do best with an Oyster card. It is difficult to say because you provide no detail. I don't know how long you may be in London. Croydon is at the extremes of the Oyster coverage. When I first read your question I thought you were coming from Gatwick, in which case it would have been very easy. I can't imagine anybody arriving at Heathrow and voluntarily staying so far away from everything as Croydon. To get to Croydon (again, which bit?) from Heathrow you could:
Take Heathrow Express to Paddington, change to the Circle line Underground (Underground and buses not included in the Britrail) to Victoria and take a Southern Train to East Croydon, West Croydon, South Croydon or any of half a dozen other stations serving bits of Croydon... or Take Heathrow Connect to Paddington and follow the above or Take either of the above to Paddington and use a taxi (not included in Britrail) to Victoria, continue as above or Take the Piccadilly Line Underground to Earls Court, change to the District Line to Victoria, continue as above. ... to be continued ...

... continued ... When you go to Kings Cross (assuming you are taking the East Coast to Edinburgh and then the connection over to Glasgow) you could take First Capitol Connect from East Croydon to Kings Cross to avoid using the Underground for that trip. If you are instead going to Glasgow via the Virgin Trains service up the West Coast which leaves from Euston Station you will need the Victoria Line from Victoria to Euston. If you want a very slow included all-train trip you could take the train from East Croydon to Watford Junction via Kensington, perhaps needing a change at Clapham Junction - you don't say what time of day nor what day of the week - and then connecting to a London Midland train to Milton Keynes and finally on to the Virgin train. Bottom line - if you provide more information you can get more specific answers. travel from London to Glasgow do I need to make a reservation for my specific day of travel? And does that ticket cost extra? If you make a reservation it would not be for the day of travel, it would be for the specific train at a specific time on the specific day. Some people get reservations, some don't. The long distance trains make them available, the short distance ones don't. They tend to be free, and must be obtained prior to travel, rules vary by train company. So, again, more information would yield you a better answer. Now for the final one. You have put your email in your post. There are known spammers who read this Helpline. There is a fair chance your e-address could be harvested. Can I suggest that you log in and edit your post and delete the email address. Anybody who wants to reply to you privately can send you what is called a PM (Private Message) which you see when you log in.